Vision assisted fixture construction

ABSTRACT

A new method and apparatus for fabrication or alignment of fixtures, jigs and structures is disclosed. The invention uses target points on one or more details which are referenced to the overall structure via targets on the details. These targets are monitored by a TV camera unit which is alternatively interfaced to a display for the human operator or a robot to provide position data. The interface may include input from a CAD system which allows display on robot coordinates to be offset by design data of the structure or a part to be located on it. 
     While mainly envisioned for assistance in constructing fixtures for automobile assembly, the disclosed invention is widely useable for all types of construction including aircraft, bridges, boats, buses, houses, buildings and the like. A means for improving resolution of automatically servoed camera based systems is also disclosed.

This is a continuation application Ser. No. 07/643,905 filed Jan. 22,1991, now abandoned; which is a continuation of 07/525,706, filed May21, 1990, now abandoned; which is a continuation of 07/382,497 filedJul. 21, 1989, now abandoned; which is a division of Ser. No. 07/113,363filed Oct. 27, 1987 now U.S. Pat. No. 4,851,905; which is a continuationof Ser. No. 07/022,596 filed Mar. 4, 1987, now abandoned; which is acontinuation of Ser. No. 06/660,279 filed Oct. 12, 1984, now abandoned.

BACKGROUND

This application incorporates by reference the following copendingapplications.

1. Targets Ser. No. 348,803 now U.S. Pat. No. 4,654,949

2. Robot Calibration Ser. No. 453,910 now U.S. Pat. No. 4,753,569

3. Pulsed Robotic Inspection now U.S. Pat. No. 4,585,350

4. Pulsed Robotic Inspection now U.S. Pat. No. 4,838,696

Copending applications by the inventor have discussed target basedguidance concepts for robot in machinery control which can lead tohigher accuracy, lower cost, higher speed and other desirable solutionsin a reliable, accurate manner capable of widespread application.

This disclosure extends this idea toward specific problems related tothe manufacture of car bodies, aircraft structures, covering and boththe assembly of the components and the fixtures that assist in thisassembly.

One embodiment of the invention aids in manufacture of fixtures. Quiteclearly, the construction of high precision fixtures for either assemblyfixtures, weld fixtures or check fixtures required by today'smanufacturer of aircraft and automobiles is an extremely expensive andtime consuming proposition. It is estimated for example that within onelarge automobile manufacturer in North America, at least $2 Billion insuch fixtures at any one time are circulating. When new car lines comeout, the fixtures for the previous line become scrap.

What's worse, the fixture costs generally have a long time delay intheir delivery. Since this is an area where numerous

engineering changes occur during the engineering of the car, widespreadlast minute changes in the fixtures are required which causes enormouscost escalations plus further adds to the delays in getting the carlines to the market which can lead to significant lost market shareconsequences.

What is disclosed herein is a novel target based technique to assist inthe construction of fixtures in either a manual or an automatic manner,greatly reducing the cost and the delivery time.

A particular area of interest is the disclosure of target basedequipment which can aid an operator or a robot in the positioning ofcheck, locating or other actual assembly details onto the fixtures aswell as the linking of such data to the CAD data systems for the partand/or fixture.

Fixtures constitute a large percentage of the cost of tooling for newbody styles and their construction interjects into any new model programa considerable time delay. Computer aided automatic vision basedmetrology systems can be utilized to materially speed up this effort toboth reduce costs and quicken the delivery time of such fixturing.

Besides the obvious increased cost effectiveness, the system proposedhas two other major advantages. First, it is directly interfaceable toCAD systems and therefore totally ameanable with future thrusts in mathmodel car design and build.

The second thing, is that the real time nature of the data providedallows the system to first be utilized in a manual mode, upward to semiautomatic and then finally to full robot fixtureless assembly using thesame basic concepts founded on metrological principles.

This proposal is generally related in some aspects to the procedure oflaying out large fabricated fixtures and other objects usingtheodolites. Such theodolites which currently have become digitized withreliable programming allow a considerable simplification of the layoutprocedure and can materially aid in the checkout of fixtures and otherstructures.

However, the use of such theodolites does very little for the personactually charged with constructing the fixture. What is proposed herehowever is a dynamic interactive target based system used by itself orin conjunction with theodolites which actually allow fabrication of theobject itself taking data concerning the part for which the fixture isto fit, such as a body side or what have you from the CAD data base andfeeding to a sensor unit that is capable of seeing the detail to beassembled and possibly the part such as a framework or other detail towhich it is to be mated.

In the first case, this allows an operator to position the detail incomputer defined space, rapidly and easily from which it would then belocked down via welding, lock screws or what have you. In addition, theprocess provides an automatic check, again relative to computer dataspace for the fixture using the part data master. In short, this is anentirely CAD compatible manufacturing process which can start outmanually--a big advantage.

In future applications, the process can be further automated with robotshandling one or more of the positioning, welding, or attaching tasks. Itis not all far removed to consider that fixtures themselves could berobot constructed.

The step beyond that is to eliminate fixtures entirely using the robotsto essentially form the fixture in a sequential mode. However, this isnot thought to be generally applicable but certainly could be applicableon certain sub assemblies, details or the like. The beauty of this wholeidea is that it can start simply off-line in the fixture build and inthe end turns out to what may be the key to the whole line itself, allthe while saving large sums of money and time.

The process is not necessarily limited solely to the fabrication offixtures. Other conveyor details including nesting fixtures, possiblyeven dies and molds could fit this as well.

This invention is illustrated in the following figures:

FIG. 1 illustrates a basic detail to fixture structure embodiment.

FIGS. 2a, 2b and 2c illustrates closeups of a detail.

FIG. 3 illustrates a display according to the invention.

FIG. 4 illustrates a robotically positioned detail.

FIG. 5 illustrates an automatic theodolite with accuracy enhanced camerasystem.

In addition, the technique here is widely useable to contruction ofstructures in general such as aircraft wing sections, houses, bridgesand anything else where detail members are to be assembled to aframework.

FIG. 1 illustrates the concept of the device. A framework, 5, let us saya weld fixture for a car, is to be set up with details which for themoment are just simply locating details which may have a complexcurvature on their face. This could however be weld guns or anythingelse for that matter.

A theodolite system or other device is utilized to establish the generalframework of the fixture in space to which the various details are to beattached. At each attaching point, a detail itself is targeted with 3 or4 dot targets.

The camera unit is pointed at the fixture detail in a known manner tothe laid out framework. This can be taken directly from the theodolitecomputers or other data entered. The details are then positioned by theoperator by looking at a screen which tells him how to position it, thedata coming from both the camera unit telling the position and the CADdata telling the desired position. When the operator has the partpositioned properly, he then locks it down using whatever means ispracticable such as spot welds, bolts, what have you.

The particularly easy thing to imagine would be locators on Gimbled orball mounts. This would allow the operator to relatively easily positionit in multi degrees of freedom under robot guidance control after whichhe would then lock it down in a more secure manner.

Reference is made to U.S. Pat. No. 4,654,959 which generally showsautomatic sensor techniques for determining target position.

The impact on production of such fixture construction is substantial. Ina large auto company alone, approximately $2 Billion in fixtures are inuse at any one time. The vast majority are scrapped when new styles areintroduced. It is estimated that this invention could save half the costof such fixtures and allow much faster delivery, assisting manufacturesin responding to market demand (for different styles, etd.). Acomparison is in order. Today the following steps are required to builda precision check fixture (e.g. for a car door).

Present Fixture Build

1. NC block (detail)

2. Scribe lines on N/C block.

3. Build up precision detail on bench (L-unit).

4. Precision mount above to precision base

5. Precision check.

With the invention, only two steps are required.

Target Fixture Build

1. NC block detail including target points.

2. Precision assembly and check (simultaneous) with camera based autotheodolite system connected to CAD design base.

Implied is much less manual labor.

Steps of operation, FIG. 1:

1. Determine location of structure frame using, for example (but notlimited to), automatic theodolite pair 10 and 11 and target points 15,16, 17, and 18 (more targets would be required if more complicated thana simple plate or rectangular frame).

2. Using computer 30 to analyze said determined target data, and inregard to design data from CAD system 40 for either the structure or apart to be held by it, derive correct location for a locator such as 50.

3. Position at least one theodolite such as 11 at a position above tosee at least two targets such as 25 and 26 on said locator (typically 3or 4 are used). This positioning can be manual or automatic from datafrom computer 30.

4. Derive from the camera 12 of said automatic theodolite at least onecoordinate of said locator relative to said camera.

5. Process the image of said camera using camera processor 13 connectedto computer 30 data to obtain location variance relative to desiredlocation.

6. Display on display 70 (or transmit--i.e. to a robot) movements neededto position locator at location desired.

Typically, theodolites 10 and 11 are placed on a floor at knownlocations relative to each other. Alternatively, they can be co-locatedon a stiff plate or other support such as 60 wheeled around for thepurpose to the job. This plate could also be overhead, (with theodolitesupside down) such as 65 shown in dotted lines, either fixed or broughtin on a slide or crane way (very desirable for floor space, but impliesautomatic operation).

Note that the NC blocks of the detail can have multiple sets of targetson different faces to allow views thereof, with each target's relationto the working surface known. For maximum visibility, targets can stickup from the surface but this can lead to damage.

FIG. 2a illustrates a closeup of a detail 100 useable on a typicalfixture. The target 101-103 points on block 105 are NC machined inrelationship with the contoured surface 110 (and perhaps on it). This isa big advantage over using hand scribed target points scribed on later.

One type of adjustable universal detail moveable in multiple axes isshown in FIG. 2b. This is capable of positioning the target block in 4-6axes (z axis slide and rotation about z axis with set screws 120 fortube 122, pitch and yaw adjustment with three screws 124, and optional xand y axes slide for base in mounting plate 126--note mounting plate 126can itself be targeted to allow for quick placement in a nearly correctposition). Other devices with ball joints etc. are also possible (e.g.115).

For automatic reading, a spot target (FIG. 2c) is better (i.e. moreaccurate) than a scribed cross hair and can be formed using retroreflective tape 170 (e.g. Scotchlite 7615) formed on a dowel pin or disc171 sunk into NC machined hole 172. If desired, contoured surface 180for locating detail can be provided with targets 182.

FIG. 3 illustrates a display 70 useable by an operator to visualize upto 6 degree of freedom data and to receive other written or pictoralmessages from the control computer 30. For best operation, displayupdate rate should be in real time (e.g. faster than 1/10 sec.) to avoidflicker. In any case, the display should show new data in less than afew seconds to avoid overly long response time.

As shown in FIG. 3, display 70 can include an actual TV image of theobject, or a solid model representation generated from CAD data andcomputer 30 to display object position in a space relative to theoperator's frame of reference such as framework 5. A bar graphicsdisplay 72 and a written message or data display 74 are also preferableincluded in display 70.

An alternative to dynamic display via real time target monitoring is totell the operator (or robot) which moves to make, which he or it thenmakes, arriving at the final position (subject to a further inspectionstep) using the accuracy of the device used to make the move, ratherthan by using the target data itself to rapidly `home in` on the finallocation. This is slower, but workable, however, it requires accuratemulti-degree of freedom positioners rather than inexpensive mounts forthe details, and it requires the positioners to be accurately locatedrelative to the overall structure, implying added target steps orprecise construction, both less desirable.

Note the display can display any or all of the following at onetime--written data, instructions, image of detail or structure, bar orother variance chart, solid model of detail, etc.

Of considerable importance is the fact that the various offset data etc.could be fed to the operator's alignment display from a CAD system. Inother words, the operator wouldn't just line up the object to be normalto the viewing axis of the camera and along its axis, but instead tocomputer generated offsets in perhaps all 6 degrees of freedom from thataxis. That axis itself would have been determined referencing from thelarger structure using the theodolite (or other means).

FIG. 4 illustrates a robot means 200 for holding a detail 201 in placewhile an operator or other robotic means locks down, the detail, e.g.with a welder 210. After lock down camera 220 verifies that the locationof the detail 201 is correct, the location is stored in memory ofcomputer 30.

FIG. 5 illustrates an automatic `theodolite` such as 500 consisting of amotorized θ and φ axes 501 and 502 equipped with high resolution angularposition sensors 505 and 506. Motors are controlled by computer 510 asis solid state TV camera 515 (e.g. a GE TN2500) via camera control 520.Linear arrays such as Reticon 1024G can be used but are generally lessuseful as they only see in one plane.

While normally used for target location, the camera can also be used tosee other features of an object or structure such as pertinent holelocations, edges, corners or the like (for example, hole 98 or corner 99of structure 51). Indeed such features once identified can be used astarget points for the purposes of this invention. Normally, however,precision special target points such as shown in FIGS. 2, 2a, 2b, and 2cwhich are either retro reflective or actively lit, for example via fiberoptics wherein an end of the fiber constitutes the target (see U.S. Pat.No. 4,654,949), offer much higher contrast and accuracy, and by theircontrast are clearly distinguishable as targets from the background withno identification problem.

For the most common case of retro reflective targets, a light with beamsplitter is located along camera axis to provide a good return signal.

Several techniques for accurately measuring and tracking are nowdisclosed.

First, two such theodolites as in FIG. 1, can be servoed to go to eachtarget point of a structure in sequence or separately to sequentiallytake target data. For example, if the data base of the structure isknown, each theodolite (or one individually) can be servoed to point atsay target 25 (or target set) and determine deviation from data baseprediction. Interestingly each can do it at random, matching the twotheodolites data, target for target, after the fact if desired.

Where the data base is being generated, the theodolites can servotogether by projecting a laser spot (such as 550 in FIG. 5) or otherpoint co-axially from one theodolite 552 (master) and locking the second(slave) onto that spot. When the master unit sees a target in its field,one or both can read (the laser is desirably turned off at this time)and the system proceeds.

One could clearly raster scan throughout space to find all the targetson a large structure or whatever. However, it is often easier to use acamera such as 560 operating at much less magnification, and use anintense point source 570 to illuminate the whole structure or a portion,identify (manually) say with a display 575, or automatically, and roughlocate the targets. Then the two theodolites are servoed by computer 510to find these targets which are now known in their approximatelocations.

Target designs for locators or other details can be all alike (e.g. 1/4"dots) or can be varied and indeed can be coded, either by shape,grouping or spacing (e.g. triangular target 580) to identify whichlocator is being looked at, for example this allows easy random accessof structure points by independently scanning theodolites for example.

The actual target discrimination can be done on-the-fly by pulsing thelight source 512 (strobe) to freeze the target image position on thecamera matrix array at a given point in time when angular positions areknown (i.e. at an encoder count point). Super fast bursts can be used tominimize blur using a diode laser (30 nsec burst) as the light source.Xenon strobes can be used as well.

Readout of target position on the matrix array gives target location.This is ideally done at high speed, and at high accuracy, for exampleusing the invention of Pinckney et al U.S. Pat. No. 4,219,847.

An alternate to pulsing is to continuously read target spot (or other)image positions very fast and record the spot location which correspondsto an encoder count. Often this is difficult to do, and techniques suchas shown in U.S. Pat. Nos. 4,585,350 and 4,838,696 are desirablyemployed. (The target image spots in this case are equivalent in thisregard to the triangulation spot images discussed therein.) Indeed, suchtechniques are crucial for theodolite work since very high accuracy isrequired.

Accuracy obtained can be quite high. For example, suppose the angularaxes are encoded with precise angular encoders as those made byHeindenhan good to 2 arc seconds (9.6×10⁻⁶ rad), each (an easilyobtainable figure).

The trip points are known to be good to one part in ten of this value or0.2 arc sec. (approx. 10⁻⁶). At a distance of 400 inches (approx. 10meters) this represents 4×10⁻⁶ inches.

A magnification of the camera lens system (telescope) of 30:1 means thata field of 7.5×7.5 inches can be viewed on the 0.25 inch×0.25 inchdetector array, a good choice as many details might have target clusterson 2 inch clusters, thus multiple targets can be seen in one view. UsingPinckney or other means such as U.S. Pat. No. 4,394,683 or 4,393,804 todetermine target spot location, such location can be reliably determinedto 1/5000 or better. This then is 1.25×10⁻³ inches, which at R=300inches is 4.1×10⁻⁶ rad, approximately the resolution of the trip pointof the angular encoder. At higher magnification, it could be the same.

When the theodolite is statically positioned, it seldom can point betterthan the limiting resolution (2 arc sec in the example) of its axisencoders, and this limits the control systems resulting ability to putit there any better. The read on-the-fly unit can do better than astatically positioned theodolite.

To expand on this, when reading on-the-fly, one can interpolate betweenencoder counts by:

1. Pulsing the light source precisely at an encoder count trip point andreading the TV camera (preferably a solid state array type) to pick upaccuracy of target point location.

2. By moving at a constant rotational speed, one can interpolate betweencounts, allowing the cameras to read at any desired point. Note that anauxilliary rotational or axial movement can be added (e.g. using a puzoelectric device) to read super precisely over a very small zone.

3. Storing the begining and end points at which camera data is taken,and determining the mid point of the encoder position which generally iscorresponding to the mid point of the target spot during the time ofmotion, since the target spot image can blur on camera if the lightsource is of longer duration.

The dual theodolite automatic system, when implemented with a lasersource in one theodolite, can be used for contouring an arbitrary objectby simply projecting the spot sequentially on the surface of the objectand looking at it with the other theodolite, recording the angularrelation of the two which gives the contour answer.

What is claimed is:
 1. A method of constructing a fixture having alocating member for holding an object in a predetermined position in thefixture comprising the steps of:providing a support member on thefixture; and positioning a locating member on the support member suchthat the locating member is positioned in an object-holding position tohold the object in the predetermined position, said step of positioningthe locating member on the support member comprising the steps of(a)positioning the locating member in a first position on the supportmember, (b) automatically sensing the first position of the locatingmember, (c) automatically comparing the sensed first position of thelocating member with the predetermined object-holding position of thelocating member to produce a comparison, (d) automatically generatinginstructions, utilizing the comparison, for repositioning the locatingmember from the first position to the predetermined object-holdingposition, and (e) moving the locating member to a second positionpursuant to the instructions in order to position the locating member atthe predetermined object-holding position.
 2. A method of constructing afixture as claimed in claim 1, wherein said step of positioning thelocating member on the support member further includes the steps of:(f)automatically sensing the position of the locating member in the secondposition, (g) automatically comparing the sensed second position of thelocating member with the predetermined object-holding position of thelocating member to produce a second comparison, (h) determining from thesecond comparison whether the locating member is at the predeterminedobject-holding position; and (i) if the locating member is not at thepredetermined object-holding position, repeating the moving step (e),the automatically sensing step (f), the automatically comparing step (g)and the determining step (h) for as many additional positions of thelocating member as necessary until the locating member is in thepredetermined object-holding position.
 3. A method of constructing afixture as claimed in claim 1, and further including the step of sensingpositions of reference.
 4. A method of constructing a fixture as claimedin claim 1, and further including the performing of said steps (a)through (e) for at least one additional locating member and anassociated support member and associated predetermined object-holdingposition.
 5. A method of constructing a fixture as claimed in claim 1,wherein said automatically comparing step (c) includes the step ofderiving the predetermined object-holding position from a CAD data baseof the object to be held in the fixture.
 6. A method of constructing afixture as claimed in claim 1 wherein said automatically generating step(d) includes displaying movements required for repositioning thelocating member to an operator.
 7. A method of constructing a fixture asclaimed in claim 4 wherein the at least one additional locating memberis a device for working on the held object, and further including thestep of working on the held object after the locating members arepositioned.
 8. A method of constructing a fixture as claimed in claim 1wherein said steps (a) through (e) for the locating member are performedin multiple degrees of freedom.
 9. A method of constructing a fixture asclaimed in claim 1 wherein said step of positioning the locating memberon the support member further includes the steps of:(f) attaching thelocating member to the support member when the locating member is in thepredetermined object-holding position.
 10. An apparatus for constructinga fixture for holding an object in a predetermined position comprising:afixture base, including a support member on the fixture base; a locatingmember for the support member which is contacted by the object when theobject is in the predetermined position; a positioning means forpositioning the locating member in a first position on the supportmember; a sensing means for automatically sensing the first position ofthe locating member; a comparing means for automatically comparing thesensed first position of the locating member with a predeterminedobject-holding position of the locating member to produce a comparison;and a generating means for automatically generating instructions,utilizing the comparison, for repositioning the locating member withsaid positioning means from the first position to a second positionpursuant to the instructions in order to position the locating member atthe predetermined object-holding position and to form the fixture. 11.An apparatus for constructing a fixture as claimed in claim 10 andfurther including a control means for causing: said sensing means tosense the second position of the locating member; said comparing meansto automatically compare the sensed second position of the locatingmember with the predetermined object-holding position of the locatingmember to produce a second comparison; a determining means to determinefrom the second comparison whether the locating member is at thepredetermined object-holding position; and if the locating member is notat the predetermined object-holding position, said generating means toautomatically generate instructions, using the second comparison, forrepositioning the locating member from the second position to a thirdposition pursuant to the instructions.
 12. An apparatus for constructinga fixture as claimed in claim 10 and further including a sensing meansfor sensing positions of reference.
 13. An apparatus for constructing afixture as claimed in claim 11, and further including at least onesecond support member on the fixture base and an associated secondlocating member, and wherein said control means also controls thepositioning of the second locating member relative to said secondsupport member with said positioning means, said sensing means, saidcomparing means and said generating means.
 14. An apparatus forconstructing a fixture as claimed in claim 10 wherein said comparingmeans includes a deriving means for deriving the predeterminedobject-holding position from a CAD data base of the object to be held inthe fixture.
 15. An apparatus for constructing a fixture as claimed inclaim 10 wherein said generating means includes a displaying means fordisplaying movements required for repositioning the locating member toan operator.
 16. An apparatus for constructing a fixture as claimed inclaim 13 wherein the at least one second locating member is a workingmeans for working on the held object after the locating members arepositioned.
 17. An apparatus for constructing a fixture as claimed inclaim 10 wherein said positioning means, said sensing means, saidcomparing means and said generating means operate in multiple degrees offreedom.
 18. An apparatus for constructing a fixture as claimed in claim10 and further including an attaching means for attaching the locatingmember to the support member when the locating member is in thepredetermined object-holding position.
 19. A method of constructing afixture having a locating member for holding an object in apredetermined position in the fixture comprising the steps of:providinga support member of the fixture; positioning a locating member on thesupport member such that the locating member is positioned in anobject-holding position to hold the object in the predeterminedposition, the locating member having at least one fixed targetpositioned thereon which is capable of being optically sensed, said stepof positioning the locating member on the support member comprising thesteps of(a) positioning the locating member in a first position on thesupport member, (b) automatically sensing the position of the at leastone target of the locating member when the locating member is in thefirst position, (c) automatically comparing the sensed position of theat least one target of the locating member in the first position with apredetermined reference position of the at least one target to produce acomparison, the reference position being the position at which the atleast one target will be when the locating member is in thepredetermined object-holding position, (d) automatically generatinginstructions, utilizing the comparison, for repositioning the locatingmember from the first position to the predetermined object-holdingposition, and (e) moving the locating member to a second positionpursuant to the instructions in order to position the locating member atthe predetermined object-holding position; and securing the locatingmember to the support member in the object-holding position.
 20. Amethod of constructing a fixture as claimed in claim 19 wherein saidstep of positioning the locating member on the support member furtherincludes the steps of:(f) automatically sensing the position of the atleast one target when the locating member is in the second position, (g)automatically comparing the sensed position of the at least one targetof the locating member in the second position with the predeterminedreference position of the at least one target to produce a secondcomparison, (h) determining from the second comparison whether thelocating member is at the predetermined object-holding position, and (i)if the locating member is not at the predetermined object-holdingposition, repeating the moving step (e), the automatically sensing step(f), the automatically comparing step (g) and the determining step (h)for as many additional positions of the locating member as necessaryuntil the locating member is in the predetermined object-holdingposition.
 21. A method of constructing a fixture as claimed in claim 19wherein there are a plurality of the targets positioned on the locatingmember, and wherein said sensing step (b) senses the plurality oftargets and said comparing step (c) compares the sensed positions of theplurality of targets with reference positions thereof.
 22. A method ofconstructing a fixture as claimed in claim 19 and further including thestep of sensing positions of reference.
 23. A method of constructing afixture as claimed in claim 22 wherein said sensing of positions ofreference step includes the viewing of an optically visible feature. 24.A method of constructing a fixture as claimed in claim 19 and furtherincluding the performing of said steps (a) through (e) for at least oneadditional locating member and an associated support member andassociated predetermined object-holding position.
 25. A method ofconstructing a fixture as claimed in claim 19 wherein said automaticallycomparing step (c) includes the step of deriving the predeterminedreference position and object-holding position from a CAD data base ofthe object to be held in the fixture.
 26. A method of constructing afixture as claimed in claim 19 wherein said automatically generatingstep (d) includes displaying movements required for repositioning thelocating member to an operator.
 27. A method of constructing a fixtureas claimed in claim 24 wherein the at least one additional locatingmember is a device for working on the held object, and further includingthe step of working on the held object after the locating members arepositioned.
 28. A method of constructing a fixture as claimed in claim19 wherein said steps (a) through (e) for the at least one target andlocating member are performed in multiple degrees of freedom.
 29. Amethod of constructing a fixture as claimed in claim 19 wherein saidsensing step includes the step of positioning the target for viewingfrom multiple directions.
 30. A method of constructing a fixture asclaimed in claim 19 wherein said sensing step includes the step ofviewing the target with at least one TV camera.
 31. A method ofconstructing a fixture as claimed in claim 24 and further including thestep of coding the target of each associated locating member differentlyso that the locating member can be identified with the coded target. 32.An apparatus for constructing a fixture for holding an object in apredetermined position comprising:a fixture base, including a supportmember on the fixture base; a locating member for the support memberwhich is contacted by the object when the object is in the predeterminedposition; at least one fixed target positioned on the locating memberwhich is capable of being optically sensed; a positioning means forpositioning the locating member in a first position on the supportmember; a sensing means for automatically sensing the position the atleast one target of the locating member when the locating member is inthe first position; a comparing means for automatically comparing thesensed position of the at least one target of the locating member in thefirst position with a predetermined reference position of the at leastone target to produce a comparison, the reference position being theposition at which the at least one target will be when the locatingmember is in the predetermined object-holding position; a generatingmeans for automatically generating instructions, utilizing thecomparison, for repositioning the locating member with said positioningmeans from the first position to a second position pursuant to theinstruction in order to position the locating member at thepredetermined object-holding position; and a securing means for securingthe locating member to the support member in the object-holding positionto form the fixture.
 33. An apparatus for constructing a fixture asclaimed in claim 32 and further including a control means for causing:said sensing means to sense the position of the at least one target whenthe locating member is in the second position; said comparing means toautomatically compare the sensed position of the at least one target ofthe locating member in the second position with the predeterminedreference position of the at least one target to produce a secondcomparison; a determining means to determine from the second comparisonwhether the locating member is at the predetermined object-holdingposition; and if the locating member is not at the predeterminedobject-holding position, said generating means to automatically generateinstructions, using the second comparison, for repositioning thelocating member from the second position to a third position pursuant tothe instructions.
 34. An apparatus for constructing a fixture as claimedin claim 32 wherein there are a plurality of the targets positioned onthe locating member, wherein said sensing means senses the plurality oftargets, and wherein said comparing means compares the sensed positionsof the plurality of targets with reference positions thereof.
 35. Anapparatus for constructing a fixture as claimed in claim 32 and furtherincluding a sensing means for sensing positions of reference.
 36. Anapparatus for constructing a fixture as claimed in claim 35 wherein saidsensing means for sensing positions of reference includes a viewingmeans for viewing of an optically visible feature.
 37. An apparatus forconstructing a fixture as claimed in claim 33 and further including atleast one second support member on the fixture base and an associatedsecond locating member with a fixed target positioned on the secondlocating member, and wherein said control means also controls thepositioning of the second locating member relative to said secondsupport member with said positioning means, said sensing means, saidcomparing means and said generating means.
 38. An apparatus forconstructing a fixture as claimed in claim 32 wherein said comparingmeans includes a deriving means for deriving the predetermined referenceposition and object-holding position from a CAD data base of the objectto be held in the fixture.
 39. An apparatus for constructing a fixtureas claimed in claim 32 wherein said generating means includes adisplaying means for displaying movements required for repositioning thelocating member to an operator.
 40. An apparatus for constructing afixture as claimed in claim 37 wherein the at least one second locatingmember is a working means for working on the held object after thelocating members are positioned.
 41. An apparatus for constructing afixture as claimed in claim 32 wherein said positioning means, saidsensing means, said comparing means and said generating means for the atleast one target and locating member operate in multiple degrees offreedom.
 42. An apparatus for constructing a fixture as claimed in claim32 wherein the targets are positioned for viewing from multipledirections.
 43. An apparatus for constructing a fixture as claimed inclaim 32 wherein said sensing means includes at least one TV camera forviewing the target.
 44. An apparatus for constructing a fixture asclaimed in claim 37 wherein the target of each associated locatingmember is differently coded so that the locating member can beidentified with the coded target.
 45. A method of constructing astructure having a detail member in a predetermined position on a basemember of the structure comprising the steps of:providing a base memberof the structure; and positioning a detail member on the base membersuch that the detail member is positioned in the predetermined position,said step of positioning the detail member on the base member comprisingthe steps of(a) positioning the detail member in a first position on thebase member, (b) automatically sensing the first position of the detailmember, (c) automatically comparing the sensed first position of thedetail member with the predetermined position of the detail member toproduce a comparison, (d) automatically generating instructions,utilizing the comparison, for repositioning the detail member from thefirst position to the predetermined position, and (e) moving the detailmember to a second position pursuant to the instructions in order toposition the detail member at the predetermined position.
 46. A methodof constructing a structure as claimed in claim 45 wherein said step ofpositioning the detail member on the base member further includes thesteps of:(f) automatically sensing the position of the detail member inthe second position, (g) automatically comparing the sensed secondposition of the detail member with the predetermined position of thedetail member to produce a second comparison, (h) determining from thesecond comparison whether the detail member is at the predeterminedposition; and (i) if the detail member is not at the predeterminedposition, repeating the moving step (e), the automatically sensing step(f), the automatically comparing step (g) and the determining step (h)for as many additional positions of the detail member as necessary untilthe detail member is in the predetermined position.
 47. A method ofconstructing a structure as claimed in claim 45 and further includingthe step of sensing positions of reference.
 48. A method of constructinga structure as claimed in claim 45 and further including the performingof said steps (a) through (e) for at least one additional detail memberand an associated base member and associated predetermined position. 49.A method of constructing a structure as claimed in claim 45 wherein saidautomatically comparing step (c) includes the step of deriving thepredetermined position from a CAD data base of the structure.
 50. Amethod of constructing a structure as claimed in claim 45 wherein saidautomatically generating step (d) includes displaying movements requiredfor repositioning the detail member to an operator.
 51. A method ofconstructing a structure as claimed in claim 48 wherein the at least oneadditional detail member is a device for working on the first-mentioneddetail member, and further including the step of working on thefirst-mentioned detail member after the at least one additional detailmembers is positioned.
 52. A method of constructing a structure asclaimed in claim 45 wherein said steps (a) through (e) for the detailmember are performed in multiple degrees of freedom.
 53. A method ofconstructing a structure as claimed in claim 45 wherein said step ofpositioning the detail member on the base member further includes thesteps of:(f) attaching the detail member to the base member when thedetail member is in the predetermined position.
 54. An apparatus forconstructing a structure comprising:a base member of the structure; adetail member for the base member to be positioned in a predeterminedposition relative to the base member; a positioning means forpositioning the detail member in a first position on the base member; asensing means for automatically sensing the first position of the detailmember; a comparing means for automatically comparing the sensed firstposition of the detail member with the predetermined position of thedetail member to produce a comparison; and a generating means forautomatically generating instructions, utilizing the comparison, forrepositioning the detail member with said positioning means from thefirst position to a second position pursuant to the instructions inorder to position the detail member at the predetermined position and toform the structure.
 55. An apparatus for constructing a structure asclaimed in claim 54 and further including a control means for causing:said sensing means to sense the second position of the detail member;said comparing means to automatically compare the sensed second positionof the detail member with the predetermined position of the detailmember to produce a second comparison; a determining means to determinefrom the second comparison whether the detail member is at thepredetermined position; and if the detail member is not at thepredetermined position, said generating means to automatically generateinstructions, using the second comparison, for repositioning the detailmember from the second position to a third position pursuant to theinstructions.
 56. An apparatus for constructing a structure as claimedin claim 54 and further including a sensing means for sensing positionsof reference.
 57. An apparatus for constructing a structure as claimedin claim 35 and further including at least one second detail member tobe positioned relative to the base member, and wherein said controlmeans also controls the positioning of the second detail member relativeto said base member with said positioning means, said sensing means,said comparing means and said generating means.
 58. An apparatus forconstructing a structure as claimed in claim 54 wherein said comparingmeans includes a deriving means for deriving the predetermined positionfrom a CAD data base of the structure.
 59. An apparatus for constructinga structure as claimed in claim 54 wherein said generating meansincludes a displaying means for displaying movements required forrepositioning the detail member to an operator.
 60. An apparatus forconstructing a structure as claimed in claim 57 wherein the at least onesecond detail member is a working means for working on thefirst-mentioned detail member after the first-mentioned detail member ispositioned.
 61. An apparatus for constructing a structure as claimed inclaim 54 wherein said positioning means, said sensing means, saidcomparing means and said generating means operate in multiple degrees offreedom.
 62. An apparatus for constructing a structure as claimed inclaim 54 and further including an attaching means for attaching thedetail member to the base member when the detail member is in thepredetermined position.